Zirconia-based sintered parts are commonly used for the manufacture of decorative articles such as jewelry, watches, bracelets, brooches, tiepins, chains, handbags, telephones, items of furniture or household tools.
To obtain a color, a pigment may be added. For example, WO 2010/024 275 describes a stabilized zirconia product which may contain between 1% and 30% alumina, incorporating a pigment based on cobalt oxide and chromium oxide, nickel oxide or iron oxide. JP 2005/306 678 and JP 2004/059 374 provide other examples of pigments.
Alumina-zirconia products, in particular those with an alumina content of between 10% and 50%, are known as having good mechanical properties, especially in terms of hardness and mechanical strength.
However, a pigment added to an alumina-zirconia product generally has a tendency to become degraded on sintering of the alumina-zirconia due to the high sintering temperatures required, which may lead to a color change that is difficult to control.
Alumina-zirconia products intended to be decorative articles must also have good scratch resistance and impact strength, and also a good appearance with well developed and uniform colors. They should also be biocompatible, i.e. they should not contain elements that might be released and that might be hazardous to man.
There is an ongoing need for novel alumina-zirconia-based ceramic sintered parts which have these properties and for novel processes for manufacturing such parts.
One aim of the invention is at least partially to satisfy this need.